Chemical solutions may be mixed either manually by a chemist or laboratory technician or they may be mixed automatically by an automated liquid mixing device. A syringe (also known as a pipette, pipettor or a micropipettor) may be used to transfer liquid from a bottle to a location where liquids are mixed, such as a micro-well plate.
For example, FIG. 1A shows prior art syringe 5 positioned over bottle 1B containing a liquid. In FIG. 1B, a technician has immersed the tip of syringe 5 into the liquid in bottle 1B. In FIG. 1C, the technician has pulled upward on plunger 6 with one hand while holding the bottom part of syringe 5 down with the other hand. Pulling upward on plunger 6 draws liquid into syringe 5. Syringe 5 can now be used for liquid dispensing.
There are problems with the prior art method of liquid dispensing illustrated in FIGS. 1A-1C. To draw liquid into the syringe it is only necessary to slightly immerse the tip of the syringe below the level of the liquid surface, as shown in FIG. 1D. However, a technician will typically over-immerse the syringe into the liquid. For example, as shown in FIG. 1C, the end of syringe 5 has been immersed far below the surface of the liquid in bottle 1B. As a result, after syringe 5 is removed from the liquid in bottle 1B, there will be an unnecessarily large amount of liquid adhered to the outside surface of syringe 5. This liquid can drip off, causing a mess and possibly causing contamination in the laboratory.
There are also similar problems with prior art automated liquid mixing devices. As with the manual method, prior art automated pipettors are ineffective at placing the syringe at the optimum level inside bottle 1B to prevent unnecessary liquid adhesion to the outside surface of syringe 5. The challenge for the prior art automated systems has been that as liquid is gradually removed from its bottle, the surface level of the liquid inside the bottle gradually decreases. Prior art systems have been unsuccessful in adjusting the degree to which the syringe is inserted into the bottle to appropriately account for the varying amount of liquid inside the bottle.
What is needed is a better liquid dispensing device.